Virtually all down size computer equipment and small electronic equipment incorporate cooling fans that are continuously energized with the electrical equipment to remove heat that is developed in the electrical circuitry during operation of the equipment. Since the electrical equipment is typically of small size and of light weight, it is desirable that a cooling fan for the equipment also be of light weight.
While the present invention is discussed herein particularly as it relates to electrically energized computer fans, it is not intended to limit utilization of the invention exclusively to computers, it being obvious that the brushless DC fan motor of this invention may find effective use in conjunction with other electrical equipment and may be employed other than to drive a cooling fan. For purposes of simplicity, this invention is discussed herein particularly as it relates to small, light weight electrically energized fans for cooling down sized computers.
Earlier fan motors of similar construction and utilization employ a solid ring of alternating polarity magnets which add weight and cost to the particular fan unit that is involved. These earlier fan motors also typically detect and employ the Hall effect current to commutate the coil or coils. The Hall effect is described as the change of the electrical conduction caused by that component of the magnetic field vector applied normal to the current density vector, which causes the angle between the current density vector and the electric field to change from the magnitude that existed prior to the induction of the magnetic field. The additional circuitry required for detection employment of the Hall effect obviously adds to the expense and detracts from commercial feasibility of the particular motor that is involved. A parking magnet has also been utilized in at least one type of electrically energized fan motor to index the fan disc in order to initiate rotation and to control the direction of motor rotations at start up. Specifically, prior art patents disclosing these particular fan motor designs are depicted particularly by U.S. Pat. Nos. 4,553,075 and 4,563,622. These fan motors each utilize a single electromagnetic coil which should produce uneven magnetic forces on the fan disc resulting in torque/flutter. This induces vibrations as the fan motor unit is operated, which vibration causes obvious mechanical problems with the fan motor itself and with the electrical equipment with which the fan motor is employed. It is desirable, therefore to provide a novel, electrically energized direct current fan motor unit employing a plurality of coils and permanent magnets for operation thereof and which is designed to minimize or eliminate the introduction of torque/flutter and vibration that would otherwise be present. It is also desirable to provide an electrically energized fan motor system that does not require the presence of a Hall effect circuit and large, annular permanent magnets for operation of the motor.
In conventional electric motors a commutator and brush system is employed for sequentially activating the coils and thereby develop the electromotive force for motor operation. In addition to the weight established by large permanent magnets and large electrical coils, the presence of a commutator and brush system for coil activation also significantly adds to the weight and expense of the electric motor system. It is desirable, therefore, to provide a novel brushless electric motor which functions responsive to direct current to drive an air blower fan or other suitable equipment. It is desirable to provide a novel electric motor system wherein solid state switching is employed for the control of sequential coil activation to thereby provide the electromotive force necessary for motor operation.
Fans for computers and other electrical equipment are typically quite noisy due to the presence of torque/flutter, vibration, turbulence and acoustical noise. It is desirable to provide a novel electric fan motor system that is of quite simple nature and does not develop significant noise and vibration during operation thereof.
Many fan motors in use at the present time for cooling of computers and other electrical equipment incorporate central hub motors of significantly large size and thereby require the fan itself to be of large size to accommodate sufficient openings for movement of a desired volume of air for cooling. It is desirable therefor to minimize the physical size of the central hub portion of the fan system, thereby allowing the fan to be of relatively small dimension and yet define an air flow opening of sufficient dimension for efficient air flow at a desired rate for efficient cooling.